| 1. |
- Acharya, S, et al.
(författare)
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The ALICE transition radiation detector: Construction, operation, and performance
- 2018
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 881, s. 88-127
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Tidskriftsartikel (refereegranskat)abstract
- The Transition Radiation Detector (TRD) was designed and built to enhance the capabilities of the ALICE detector at the Large Hadron Collider (LHC). While aimed at providing electron identification and triggering, the TRD also contributes significantly to the track reconstruction and calibration in the central barrel of ALICE. In this paper the design, construction, operation, and performance of this detector are discussed. A pion rejection factor of up to 410 is achieved at a momentum of 1 GeV/c in p-Pb collisions and the resolution at high transverse momentum improves by about 40% when including the TRD information in track reconstruction. The triggering capability is demonstrated both for jet, light nuclei, and electron selection. © 2017 CERN for the benefit of the ALICE Collaboration.
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| 2. |
- Aggarwal, M.M, et al.
(författare)
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Particle identification studies with a full-size 4-GEM prototype for the ALICE TPC upgrade
- 2018
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 903, s. 215-223
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Tidskriftsartikel (refereegranskat)abstract
- A large Time Projection Chamber is the main device for tracking and charged-particle identification in the ALICE experiment at the CERN LHC. After the second long shutdown in 2019/20, the LHC will deliver Pb beams colliding at an interaction rate of about 50 kHz, which is about a factor of 50 above the present readout rate of the TPC. This will result in a significant improvement on the sensitivity to rare probes that are considered key observables to characterize the QCD matter created in such collisions. In order to make full use of this luminosity, the currently used gated Multi-Wire Proportional Chambers will be replaced. The upgrade relies on continuously operated readout detectors employing Gas Electron Multiplier technology to retain the performance in terms of particle identification via the measurement of the specific energy loss by ionization dE/dx. A full-size readout chamber prototype was assembled in 2014 featuring a stack of four GEM foils as an amplification stage. The performance of the prototype was evaluated in a test beam campaign at the CERN PS. The dE/dx resolution complies with both the performance of the currently operated MWPC-based readout chambers and the challenging requirements of the ALICE TPC upgrade program. Detailed simulations of the readout system are able to reproduce the data. © 2018 Elsevier B.V.
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| 3. |
- Ahmadi Afzadi, Masoud, et al.
(författare)
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Genome-wide expression analysis suggests a role for jasmonates in the resistance to blue mold in apple
- 2018
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Ingår i: Plant growth regulation (Print). - : Springer Science and Business Media LLC. - 0167-6903 .- 1573-5087. ; 85:3, s. 375-387
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Tidskriftsartikel (refereegranskat)abstract
- Blue mold, caused by the necrotrophic fungal pathogen Penicillium expansum, causes serious postharvest losses in apple, and threatens human health through production of the potent mycotoxin patulin. Recent studies indicate a quantitative control of resistance against this disease in apple cultivars. A whole genome apple microarray covering 60k transcripts was used to identify gene(s) that appear to be differentially regulated between resistant and susceptible cultivars in P. expansum-infected fruits. A number of potential candidates was encountered among defense- and oxidative stress-related genes, cell wall modification and lignification genes, and genes related to localization and transport. Induction of one cell wall-related gene and three genes involved in the 'down-stream' flavonoid biosynthesis pathway, demonstrates the fundamental role of the cell wall as an important barrier, and suggests that fruit flavonoids are involved in the resistance to blue mold. Moreover, exogenous application of the plant hormone methyl jasmonate (MeJA) reduced the symptoms resulting from inoculating apples with P. expansum. This is the first report linking MeJA and activation of cell wall and flavonoid pathway genes to resistance against blue mold in a study comparing different cultivars of domesticated apple. Our results provide an initial categorization of genes that are potentially involved in the resistance mechanism, and should be useful for developing tools for gene marker-assisted breeding of apple cultivars with an improved resistance to blue mold.
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| 4. |
- Andersson, Joel, et al.
(författare)
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New features of the MAX IV thermionic pre-injector
- 2017
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 855, s. 65-80
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Tidskriftsartikel (refereegranskat)abstract
- The MAX IV facility in Lund, Sweden consists of two storage rings for production of synchrotron radiation. The smaller 1.5 GeV ring is presently under construction, while the larger 3 GeV ring is being commissioned. Both rings will be operating with top-up injections from a full-energy injector. During injection, the electron beam is first delivered to the main injector from a thermionic pre-injector which consists of a thermionic RF gun, a chopper system, and an energy filter. In order to reduce losses of high-energy electrons along the injector and in the rings, the electron beam provided by the thermionic pre-injector should have the correct time structure and energy distribution. In this paper, the design of the MAX IV thermionic pre-injector with all its sub components is presented. The electron beam delivered by the pre-injector and its dependence on parameters such as optics, cathode temperature, and RF power are studied. Measurements are here compared with simulation results obtained by particle tracking and electromagnetic codes. The chopper system is described in detail, and different driving schemes that optimize the injection efficiency for the two storage rings are investigated. During operation, it was discovered that the structure of the beam delivered by the gun is affected by mode beating between the accelerating and a low-order mode. This mode beating is also studied in detail. Finally, initial measurements of the electron beam delivered to the 3 GeV ring during commissioning are presented.
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| 5. |
- Bevilacqua, Riccardo, et al.
(författare)
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A procedure for the characterization of electron transmission through Frisch grids
- 2015
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 770, s. 64-67
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Tidskriftsartikel (refereegranskat)abstract
- In Frisch grid ionization chambers special attention must be paid to the operating voltages in order to avoid unwanted collection of electrons on the Frisch grid. Collection of electrons on the grid will lead to a decreased signal to noise ratio and consequently a deteriorated energy resolution. Furthermore, systematic errors in the determination of the angular distribution will be introduced. Theoretical formulas for minimized collection of electrons on the grid were derived by Bunemann et al. [3] in the special case of a Frisch grid consisting of a plane of parallel wires. No such formulas exist for other grid geometries and a careful calibration procedure is needed. We describe here a procedure for characterizing the Frisch grid in terms of its transparency to electrons for a grid consisting of a mesh of crossed wires.
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| 6. |
- Braumann, Ilka, et al.
(författare)
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Semi-dwarf barley (Hordeum vulgare L.) brh2 and ari-l mutants are deficient in a U-box E3 ubiquitin ligase
- 2018
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Ingår i: Plant Growth Regulation. - : Springer Science and Business Media LLC. - 0167-6903 .- 1573-5087. ; 86:2, s. 223-234
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Tidskriftsartikel (refereegranskat)abstract
- Lodging is the process where crop plants fall over and lie on the ground due to strong winds and heavy precipitation. This problem reduces yield and increases the risk of fungal infections and pre-harvest germination. In order to avoid lodging, plant breeders utilize short-culm mutants, which often have a robust culm that can support the weight of a heavy spike. In barley (Hordeum vulgare L.), thousands of short-culm mutants have been isolated in breeding programs around the world. Our long-term goal is to reveal the genetic network underlying culm length, with the objective to provide an enlarged repertoire of genes and alleles suitable for future breeding of lodging resistant barley. In the present work we studied a group of allelic brh2 and ari-l mutants, which have a relatively strong semi-dwarf phenotype and are phenotypically similar to previously identified mutants deficient in brassinosteroid signalling or metabolism. The Brh2 gene is located in the centromeric region of chromosome 4H and we applied a candidate gene approach to identify the gene. Brh2 is orthologous to TUD1 in rice (Orysa sativa L.), which encodes a U-box E3 ubiquitin ligase. We identified one missense mutation, one nonsense mutation and four deletions of the complete Brh2 gene. The mutants could respond to exogenously applied brassinolide, which suggests that the apparent brassinosteroid deficient phenotype of barley brh2 and ari-l mutants is related to brassinosteroid metabolism rather than signalling.
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| 7. |
- Breunlin, Jonas, et al.
(författare)
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Methods for measuring sub-pm rad vertical emittance at the Swiss Light Source
- 2015
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 803, s. 55-64
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Tidskriftsartikel (refereegranskat)abstract
- We report on methods capable of measuring a rms vertical electron beam size of 3 pm with a runs error of less than 10% at a diagnostic beamline at the Swiss Light Source (SLS). This corresponds to a vertical emittance 01 06 pm rad with a 20% rms error. We showed this capability by presenting the theoretical basis for, and the data from, a series of measurements on a stable beam at 1.6 pm rad vertical emittance at the SLS. The methods presented utilized either pi- or sigma-polarized synchrotron radiation (SR) in the visible to ultra violet (vis-UV) spectral range. In addition to the established g-polarization method, we introduced a diffraction method with a potentially high resolution capability. Also an intensity imbalanced diffraction scheme was introduced, but was found to be prone to SR induced carbon contamination on optical elements. (C) 2015 Elsevier B.V. All rights reserved.
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| 8. |
- Holm, Sonja L., et al.
(författare)
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Neutron guide-split: A high performance guide bundle concept for elliptical guides
- 2015
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 782, s. 1-8
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Tidskriftsartikel (refereegranskat)abstract
- We present a new guide-split concept for transporting cold and thermal neutrons to multiple instruments from a single beam port at a neutron facility without compromising the useful neutron brilliance notably for any of the instruments. Elliptical guides are capable of transporting an almost completely filled phase space within a large divergence (+/- 2 degrees for cold neutrons). It is therefore possible to place several secondary guides side by side pointing in slightly different directions using the end of a primary guide as a virtual source. The instruments placed at the secondary guides hence exploit different parts of the phase space transported by the primary guide. In addition, the resulting kink between the primary and secondary guide eliminates line of sight. Using ray-tracing simulations of three different set-ups (with two, four, and eight secondary guides) we show that it is possible to illuminate at least eight sample positions from one beam port with a brilliance transfer above 90% on each sample on a 150 m long instrument. This has been clone for a phase space volume comprised of an area of 1 x 1 cm(2) and a maximum divergence of +/- 0.5 degrees within a wavelength band of 425-5.75 angstrom. We show, by a full virtual experiment, an example of applying the guide-split concept to an instrument proposed for the European Spallation Source, namely a magnetism diffractometer. (C) 2015 Elsevier B.V. All rights reserved,
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| 9. |
- Jebali, R., et al.
(författare)
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A first comparison of the responses of a He-4-based fast-neutron detector and a NE-213 liquid-scintillator reference detector
- 2015
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 794, s. 102-108
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Tidskriftsartikel (refereegranskat)abstract
- A first comparison has been made between the pulse-shape discrimination characteristics of a novel He-4-based pressurized scintillation detector and a NE-213 liquicl-scintillator reference detector using an Am/Be mixed-field neutron and gamma-ray source and a high-resolution scintillation-pulse digitizer. In particular, the capabilities of the two fast neutron detectors to discriminate between neutrons and gamma-rays were investigated. The NE-213 liquicl-scintillator reference cell produced a wide range of scintillation-light yields in response to he gamma-ray field of the source. In stark contrast, clue to the size and pressure of the He-4 gas volume, the He-4-based detector registered a maximum scintillation-light yield of 750 keV(ee) to the same gamma-ray field. Pulse-shape discrimination for particles with scintillation-light yields of more than 750 keV(ee) was excellent in the case of the He-4-based detector. Above 750 keV(ee) its signal was unambiguously neutron, enabling particle identification based entirely upon the amount of scintillation light produced. (C) 2015 The Authors. Published by Elsevier B.V.
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| 10. |
- Lalovic, Natasa, et al.
(författare)
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Performance of the AGATA gamma-ray spectrometer in the PreSPEC set-up at GSI
- 2016
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576 .- 0167-5087. ; 806, s. 258-266
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Tidskriftsartikel (refereegranskat)abstract
- In contemporary nuclear physics, the European Advanced GAmma Tracking Array (AGATA) represents a crucial detection system for cutting-edge nuclear structure studies. AGATA consists of highly segmented high-purity germanium crystals and uses the pulse-shape analysis technique to determine both the position and the energy of the y-ray interaction points in the crystals. It is the tracking algorithms that deploy this information and enable insight into the sequence of interactions, providing information on the full or partial absorption of the 7 ray. A series of dedicated performance measurements for an AGATA set-up comprising 21 crystals is described. This set-up was used within the recent PreSPEC-AGATA experimental campaign at the GSI Helmholtzzentrum fur Schwerionenforschung. Using the radioactive sources Co-56, Co-60 and Eu-152, absolute and normalized efficiencies and the peak-to-total of the array were measured. These quantities are discussed using different data analysis procedures. The quality of the pulse-shape analysis and the tracking algorithm are evaluated. The agreement between the experimental data and the Geant4 simulations is also investigated.
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